Abstract

Experiments on Bénard convection are performed on silicon oil in a pentagonal vessel. Initially, a perfect convective hexagonal pattern is imposed with such an orientation that one side wall causes the appearance of orientation disorder, while the other four side walls do not perturb the pattern. The disorder first appears close to this wall and then, in the whole pattern. The amount of disorder and the wavelength are studied for the transient and the permanent states. The time evolution of the pattern depends on the distance to the threshold, but very slow or very fast evolutions are exhibited for particular values of this parameter. It is found that the final state is independent of initial conditions.